1. Field of the Invention
The present invention relates to a thin-film magnetic write head used, for example, as a floating-type magnetic head. More particularly, the invention relates to a thin-film magnetic head in which fringing flux can be produced at an appropriate section in the periphery of a gap layer and which is suitable for an increased recording density and an increased recording frequency.
2. Description of the Related Art
FIG. 23 is a partial front view showing the structure of a conventional thin-film magnetic head (inductive head), and FIG. 24 is a sectional view taken along the line XXIVxe2x80x94XXIV of FIG. 23.
As shown in FIGS. 23 and 24, an insulating layer 9 is formed on a lower core layer 1 composed of a magnetic material, such as Permalloy.
The insulating layer 9 is provided with a trench 9a which extends in the height direction (in the Y direction in the drawing) from a surface facing a recording medium (hereinafter referred to as an xe2x80x9cABSxe2x80x9d) with the inner width being set to be a track width Tw.
In the trench 9a, a lower pole layer 3, a gap layer 4, and an upper pole layer 5 which is magnetically coupled to an upper core layer 6 are formed by plating in that order from the bottom.
As shown in FIG. 23, the upper core layer 6 is formed by plating over the upper pole layer 5.
As shown in FIG. 24, a coil layer Co is spirally formed by patterning on the insulating layer 9 at the back of the trench 9a formed in the insulating layer 9.
The coil layer Co is covered by a coil insulating layer 8 composed of a resist or the like, and the upper core layer 6 is formed on the coil insulating layer 8. A tip 6a of the upper core layer 6 is magnetically coupled to the upper pole layer 5 and a base 6b of the upper core layer 6 is magnetically coupled to the lower core layer 1.
In the inductive head shown in FIGS. 23 and 24, when a recording current is applied to the coil layer Co, a recording magnetic field is induced in the lower core layer 1 and the upper core layer 6, and magnetic signals are written into a recording medium, such as a hard disk, by a fringing magnetic field between the lower pole layer 3 which is magnetically coupled to the lower core layer 1, and the upper pole layer 5 which is magnetically coupled to the upper core layer 6.
In the inductive head shown in FIGS. 23 and 24, the lower pole layer 3, the gap layer 4, and the upper pole layer 5 are locally formed with the track width in the vicinity of the ABS, and an inductive head of this type is suitable for track narrowing.
A method for fabricating the inductive head shown in FIGS. 23 and 24 will be described. First, the insulating layer 9 is formed on the lower core layer 1, and the trench 9a having the track width Tw is formed in the insulating layer 9 for a predetermined length from the ABS in the height direction.
Next, in the trench 9a, the lower pole layer 3, the gap layer 4, and the upper pole layer 5 are continuously formed by plating, and then the coil layer Co is formed by patterning on the insulating layer 9 at the back of the trench 9a formed in the insulating layer 9.
The coil layer Co is covered by the coil insulating layer 8, and the upper core layer 6 is formed over the upper pole layer 5 and the coil insulating layer 8 by frame plating, and thus the inductive head shown in FIGS. 23 and 24 is obtained.
In the thin-film magnetic head shown in FIGS. 23 and 24, as described above, when a recording current is applied to the coil layer Co, a recording magnetic field is induced in the lower core layer 1 and the upper core layer 6, and magnetic flux flows into the lower pole layer 3 and the upper pole layer 5. Consequently, the upper pole layer 5 is magnetically saturated in the vicinity of the gap layer 4, resulting in a fringing flux, and magnetic recording is performed on the recording medium by the fringing flux.
However, in the inductive head shown in FIG. 24, at the joint between the upper pole layer 5 and the upper core layer 6, the inner end of the lower surface of the upper core layer 6 and the inner end of the upper surface of the upper pole layer 5 are located at the same position.
If the inner end of the upper core layer 6 and the inner end of the upper pole layer 5 are located at the same position at the joint between the upper pole layer 5 and the upper core layer 6, flux from the upper core layer 6 cannot be concentrated at the joint and it may not be possible for the flux to magnetically saturate the upper pole layer 5, resulting in a deterioration of the recording characteristics of the inductive head.
The depth T1 in the height direction of the joint between the gap layer 4 and the upper pole layer 5 is generally referred to as a gap depth (Gd), and in order to increase the fringing flux at the gap layer 4, the gap depth T1 must be decreased.
However, in the inductive head shown in FIG. 24, the gap depth T1 is equal to the length from the front surface at the ABS to the back surface in the height direction of the upper pole layer 5.
With respect to the structure of the thin-film magnetic head shown in FIGS. 23 and 24, since the width in the track width direction (in the X direction in the drawing) of the upper core layer 6 is larger than the width in the track width direction of the upper pole layer 5, which is equal to the track width Tw, the fringing magnetic field occurring between the upper core layer 6 and the upper pole layer 5 is wider than the track width Tw, and thus side fringing easily occurs.
In order to fabricate a thin-film magnetic head which is suitable for an increased recording density, in addition to the narrowing of the track width Tw, side fringing must be suppressed.
Accordingly, it is an object of the present invention to provide a thin-film magnetic head in which accurate magnetic recording can be performed by reliably producing fringing flux at a gap layer even if the track width is decreased.
It is another object of the present invention to provide a thin-film magnetic head in which, in particular, side fringing can be appropriately suppressed and also to provide a method for fabricating the same.
In one aspect of the present invention, a thin-film magnetic head includes a lower core layer; a gap layer formed on the lower core layer directly or with a lower pole layer therebetween, the lower pole layer having a smaller width in the track width direction than that of the lower core layer; an upper pole layer formed on the gap layer, the upper pole layer having a smaller width in the track width direction than that of the lower core layer; and an upper core layer joined to the upper pole layer. In the joint between the upper pole layer and the upper core layer, the width in the track width direction of the lower surface of the upper core layer is larger than the width in the track width direction of the upper surface of the upper pole layer, and also the inner end of the lower surface of the upper core layer is located at the back, in the height direction, of the inner end of the upper surface of the upper pole layer.
In this aspect of the present invention, at the joint between the upper pole layer and the upper core layer, flux from the upper core layer can be concentrated, and thus the upper pole layer can be reliably magnetically saturated by the flux. Therefore, recording characteristics of the thin-film magnetic head can be stabilized.
Since the flux flows satisfactorily from the upper core layer to the upper pole layer, high frequency recording characteristics of the thin-film magnetic head are also improved.
Preferably, the inner end of the lower surface of the upper core layer is 0.2 xcexcm to 1.5 xcexcm distant from the inner end of the upper surface of the upper pole layer in the height direction.
Preferably, the back surface of the upper pole layer is located towards the back, in the height direction, from the depth in the height direction (gap depth) of a magnetic gap, the magnetic gap being formed by joining the upper pole layer and the gap layer together.
For example, a Gd-setting insulating layer for determining the depth in the height direction (gap depth) of the magnetic gap is provided towards the back, in the height direction, and the contact surface between the upper pole layer and the Gd-setting insulating layer is located at the back, in the height direction, of the magnetic gap.
Preferably, the gap layer is composed of a nonmagnetic metallic material formable by plating.
More preferably, the nonmagnetic metallic material is at least one material selected from the group consisting of NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
In another aspect of the present invention, a thin-film magnetic head includes a lower core layer; a recording core formed on the lower core layer and exposed at a surface facing a recording medium, the recording core including either a lower pole layer, a gap layer, and an upper pole layer deposited in that order, or the gap layer and the upper pole layer deposited in that order; an upper core layer magnetically coupled to the upper pole layer of the recording core; a coil for inducing a recording magnetic field in the lower core layer, the recording core, and the upper core layer; and a magnetic intermediate layer formed between the upper pole layer and the upper core layer, the magnetic intermediate layer having a higher saturation flux density than that of the upper core layer.
As described above, in this aspect of the present invention, the magnetic intermediate layer having a higher saturation flux density than that of the upper core layer is interposed between the upper pole layer and the upper core layer.
Consequently, a recording magnetic field flows from the upper core layer into the upper pole layer through the magnetic intermediate layer. Since the saturation flux density of the magnetic intermediate layer is higher than that of the upper core layer, the recording magnetic field from the upper core layer flows into the upper pole layer after being concentrated in the magnetic intermediate layer, and side fringing does not easily occur in comparison with the conventional thin-film magnetic head. Moreover, it is possible to improve recording efficiency by providing the magnetic intermediate layer. As described above, in this aspect of the present invention, side fringing can be suppressed and recording efficiency can be appropriately improved, and thus it is possible to obtain a thin-film magnetic head which is suitable for an increased recording density.
Preferably, the width in the track width direction of the magnetic intermediate layer is smaller than the width in the track width direction of the upper core layer. Consequently, since it is possible to further concentrate a fringing magnetic field from the upper core layer in the vicinity of the gap, side fringing can be suppressed and also recording efficiency can be improved.
Preferably, the width in the track width direction of the magnetic intermediate layer is smaller than the width in the track width direction of the upper pole layer. Consequently, since it is possible to further concentrate a fringing magnetic field from the upper core layer in the vicinity of the gap, side fringing can be suppressed and also recording efficiency can be improved.
In the structure described above, the front surface at the recording medium side of the magnetic intermediate layer may be exposed at the surface facing the recording medium. Since the width in the track width direction of the magnetic intermediate layer is smaller than the width in the track width direction of the upper pole layer, even if the magnetic intermediate layer is exposed at the surface facing the recording medium, the recording magnetic field is appropriately concentrated in the vicinity of the gap, and thus side fringing does not increase and also recording efficiency is not degraded.
Preferably, the front surface at the recording medium side of the magnetic intermediate layer recedes in the height direction from the surface facing the recording medium.
By making the front surface of the magnetic intermediate layer recede from the surface facing the recording medium in the height direction, even if the width in the track width direction of the magnetic intermediate layer is larger than the width in the track width direction of the upper pole layer and a portion of the fringing magnetic field produced between the magnetic intermediate layer and the upper pole layer occurs slightly wider than the track width Tw, the fringing magnetic field is not detected as side fringing, and thus it is possible to more appropriately suppress side fringing.
Preferably, the front surface at the recording medium side of the upper core layer recedes in the height direction from the surface facing the recording medium. Consequently, the recording magnetic field can be more appropriately concentrated in the vicinity of the gap, and thus side fringing can be effectively suppressed.
Preferably, the saturation flux density of the magnetic intermediate layer is 1.3 T or more. More preferably, the magnetic intermediate layer is composed of FeNi, where the Fe content is 40 to 90% by mass and the balance is the Ni content. Such a magnetic material has a saturation flux density of 1.3 T or more.
In another aspect of the present invention, a method for fabricating a thin-film magnetic head includes:
a step (a) of forming a recording core on a lower core layer, the recording core including either a lower pole layer, a gap layer, and an upper pole layer deposited in that order, wherein the layers define the widths in the track width direction of the lower pole layer and the upper pole layer, at a surface facing a recording medium; or a gap layer and an upper pole layer deposited in that order, wherein the layers define the width in the track width direction of the upper pole layer at a surface facing a recording medium;
a step (b) of forming an insulating layer in the periphery of the recording core prior to or subsequent to the step (a) so that the upper surface of the recording core and the upper surface of the insulating layer are at the same level;
a step (c) of forming a magnetic material layer having a higher saturation flux density than that of an upper core layer on the recording core and the insulating layer;
a step (d) of forming a resist layer with a predetermined size on the magnetic material layer so as to cover at least a portion of the magnetic material layer formed on the recording core;
a step (e) of removing the magnetic material layer in the portion not covered by the resist layer so as to form a magnetic intermediate layer from the remaining magnetic material layer; and
a step (f) of removing the resist layer on the magnetic intermediate layer and forming the upper core layer on the magnetic intermediate layer by patterning.
Alternatively, in another aspect of the present invention, a method for fabricating a thin-film magnetic head includes:
a step (a) of forming a recording core on a lower core layer, the recording core including either a lower pole layer, a gap layer, and an upper pole layer deposited in that order, wherein the layers define the widths in the track width direction of the lower pole layer and the upper pole layer, at a surface facing a recording medium; or a gap layer and an upper pole layer deposited in that order, wherein the layers define the width in the track width direction of the upper pole layer at a surface facing a recording medium;
a step (b) of forming an insulating layer in the periphery of the recording core prior to or subsequent to the step (a) so that the upper surface of the recording core and the upper surface of the insulating layer are at the same level;
a step (g) of forming a resist layer on the recording core and the insulating layer, and making a pattern for forming a magnetic intermediate layer in the resist layer so that at least a portion of the recording core is exposed in the pattern;
a step (h) of forming the magnetic intermediate layer in the pattern, the magnetic intermediate layer having a larger saturation flux density than that of an upper core layer;
a step (i) of removing the resist layer; and
a step (j) of forming the upper core layer on the magnetic intermediate layer by patterning.
In accordance with either one of the fabrication methods described above, it is possible to appropriately form the magnetic intermediate layer with a high degree of consistency. Additionally, by interposing the magnetic intermediate layer between the upper pole layer and the upper core layer, it is possible to obtain satisfactory magnetic coupling between the upper pole layer and the upper core layer.
Preferably, the width in the track width direction of the resist layer in the step (d) or the width in the track width direction of the pattern in the step (g) is smaller than the width in the track width direction of the upper core layer so that the width in the track width direction of the magnetic intermediate layer is smaller than the width in the track width direction of the upper core layer.
As described above, in the present invention, the pattern of the resist layer can be set at a predetermined size, and in the case described above, the width in the track width direction of the magnetic intermediate layer can be set smaller than the width in the track width direction of the upper core layer. Consequently, a recording magnetic field can be concentrated in the vicinity of the gap, and it is possible to obtain a thin-film magnetic head in which side fringing can be more appropriately suppressed.
Preferably, the width in the track width direction of the resist layer in the step (d) or the width in the track width direction of the pattern in the step (g) is smaller than the width in the track width direction of the upper pole layer so that the width in the track width direction of the magnetic intermediate layer is smaller than the width in the track width direction of the upper pole layer.
As described above, in the present invention, the width in the track width direction of the magnetic intermediate layer can be set smaller than the width in the track width direction of the upper pole layer. Consequently, the recording magnetic field can be further concentrated in the vicinity of the gap, and it is possible to obtain a thin-film magnetic head in which side fringing can be more appropriately suppressed.
In the structure described above, more preferably, the front surface at the recording medium side of the resist layer in the step (d) or the front surface at the recording medium side of the pattern in the step (g) is formed along the surface facing the recording medium so that the front surface at the recording medium side of the magnetic intermediate layer is exposed at the surface facing the recording medium.
Preferably, the front surface at the recording medium side of the resist layer in the step (d) or the front surface at the recording medium side of the pattern in the step (g) recedes in the height direction from the surface facing the recording medium so that the front surface at the recording medium side of the magnetic intermediate layer recedes in the height direction from the surface facing the recording medium. Consequently, even if a portion of a fringing magnetic field produced between the magnetic intermediate layer and the upper pole layer has a larger width than the track width Tw, side fringing does not easily occur.
Preferably, in the step (f) or in the step (j), the front surface at the recording medium side of the upper core layer recedes in the height direction from the surface facing the recording medium. Consequently, the recording magnetic field can be more effectively concentrated in the vicinity of the gap, and side fringing can be appropriately suppressed.
Preferably, the magnetic intermediate layer is composed of FeNi, where the Fe content is 40 to 90% by mass and the balance is the Ni content.